I have been agonising for months over how deeply to get into imaging, and have reluctantly decided to limit myself to stacking a few subs in
DSS, and using the RGB, luminance, and saturation sliders therein.
No darks , flats, biases, deconvolution, binning etc. I have tried and tried
to get my poor old head around it all, and failed dismally. If I don't perform any particular operation frequently, I have to learn how to do it all over again. An example is when I save an image to my desktop from
DSS with changes embedded but not applied, I can't remember how to
apply those embedded changes later.
Having said all that, here is my first effort at a stacked nebula.
2 subs 25 and 30secs. ISO 6400[I will reduce that as I improve].
raymo
Looks ok for 55secs. Take some more subs and stack them all together. The more the better.
Darks and bias frames are very easy to take. Just put the lense cap on the camera or ota and take images. For darks use the same duration and iso settings as your light frames and bias frames you use the shortest exp time you can. Flats frames are a little more complicated and requires a uniform light source such as the sky at dawn or dusk or a light box/panel. Then its just a matter of playing with exp time to get an image with about 30,000 adu's.
Then just add them all into your stacking program.
Thanks for reply. I know how to take darks, flats etc. I've decided not to
do it, as I won't be doing any further processing after DSS, and the noise
reduction function in camera does quite a good job. I intend to reduce the ISO which will of course reduce the noise. I'm pushing 80 and the computers are doing my head in, as the youngsters say.
Thanks again.
That's a good first effort.
what scope, mount and camera are you using?
are you guiding?
you don't really have to worry about noise if you're exposing only for 30secs to 1min.
I would suggest, first try and see what length of sub you can get without stars trailing in the centre.
if that is say 90 seconds, then try iso 3200 with that but take more of them.
if you can get 120seconds without trailing the centre, then drop the iso to 1600.
the limiting factor here is your guiding and star trails more than noise.
Noise in dslr's usually show up after 3 to 5 minutes depending on ambient temperature and camera model and can easily be removed with darks.
since we don't always have clear skies, rather than lose time taking auto camera darks after each exposure or camera noise reduction, take a series of subs, and then you can take darks even if clouds roll in.
that way you won't lose clear skies.
Its a lot easier to manipulate the image in free software like gimp although there will be limitations as its only 8 bit. but should be ample to give you good control over brightness and contrast.
DSS does a good job as well but is a bit tricky to make fine adjustments.
when saving the file, there should be a tickbox to embed saved changes.
you will need a coma corrector as well and that will fix the coma at the edges. the baader mpcc does a very good job if you get the spacing correct.
Hi Alistair, Thanks for the encouragement; I use an 8"f5 Newt on an
HEQ5 Pro with 1100D camera. Sometimes I use an 80mm refr.
I have been astro imaging for well over 50yrs, but high quality digital
imaging [actually, the processing] has proven to be well beyond what
my poor old brain can cope with; and my wife gets fed up with all the hours I spend on the computer trying to nut it out, let alone actually doing it. I know I need a coma corrector, but I can't afford one. I can't afford an auto guider either, but I'm actually glad because I can do without the agro of learning to use it and it's associated software.
Incidentally, I know how to embed images, but have no idea how to apply the embedded changes later. The image with embedded changes
shows up in the appropriate file, but is in original form, so I am
having to save images with changes applied.[ I haven't worried about
accurate PA for longer exposures until I get everything else working right,
and no I'm not guiding, although I did manually guide for many many years].
raymo
Last edited by raymo; 21-01-2014 at 04:12 PM.
Reason: more information
A simple document with screenshots of DSS showing how to stack and export the file should help you as a reference.
I'll see if I can write one up for you.
Are you imaging from dark skies? reason I ask is if you are, then you could use a modified web cam that comes up in the classifieds for guiding.
I know Meru here used a logitech webcam for guiding. they are usually under $30.
Otherwise, if you spend a reasonable amount of time polar aligning and leave your scope and mount outside, that will help you go unguided for longer.
There is a dedicated thread in one of the UK forums for unguided imaging where they image for upto 1 hour unguided, of course much better mounts, but it is possible and polar alignment is key.
you should be able to get atleast 2 min unguided without PEC if your PA is good.
I dont want to complicate things too much but if you install teamviewer which is a remote control software, someone you know here can remotely show you how to process and will save you loads of time.
generally, DSLR images are a lot easier to process than CCD's as they're already stretched.
so all you need is to register and stack in DSS, and do some basic contrast/colour correction in gimp.
have you looked for videos on youtube that show how its done? that will give you pointers as well.
but since you mentioned you don't always recall the steps, a printed guide will surely help.
Rather than spending time adjusting the image in DSS, do try opening it with the Canon software that would've come with your 1100D on a CD.
That has colour correction tools and is quite easy and intuitive
Are you able to post just the stacked image without any adjustments here?
As for coma, there are software tools that allow you to "pinch" the image so it removes coma to a small extent. you can then crop it.
What refractor do you have, what is its focal ratio?
You certainly have an ability for squeezing out everything the image has to give. The image looks great for the allotted time. But why only 2 subs? More subs = less noise and more signal. DSS will track and stack even if they move from one frame to the next.
I'm overwhelmed by all the suggestions, offers, ideas etc. My 80mm
is just an f5 achro from SW which I bought more for the tripod than the scope; the focuser is absolute crap, but the colour correction is very
good for an achro. It was $199. GREAT solid tripod with slow motions.
Only 2 subs because no recent chance to do some imaging, so looked through my files and saw those 2 and wondered what stacking would
do for them.
I'm not imaging from dark skies, living on the edge of town, and have
2 streetlamps within about 25 metres and 2 more within about 40metres.
I'll stack those 2 images again, downsize the image, and post it.
I'll try the Canon software..
I'm quite happy to manually guide again; with modern exposure times
it's a doddle.
I really don't want to go deeper into processing at this stage.
Yes, I know DSS stacks moving objects, one of the clusters I posted
earlier was about 25 frames done in DSS. I discovered that the HDR
software Picturenaut won't do that.
Thanks again
raymo
when using my goto dob with dslr i only go to 20 seconds @ iso 3200, i found it gives a reasonable balance and can give good results on the medium to brighter DSOs. the only additional frames i took were darks, as you know how to take them it is worth adding them in DSS (you don't need to do it in another program). after you select the subs, all you need to do is 'select dark frames' from the menu on the left and select the files that they are DSS takes care of the rest. they definitely make an improvement on the image.
good job, keep at it, some more subs and darks will make a massive improvement. I'm amazed you could get that result from the image manipulation tools in DSS! I find it really slows down my computer and makes it really impossible to see the changes in 'real time.'
Thanks Jo and Rusty. If you are surprised at what I did with DSS,
consider that my laptop is about 8yrs old, has the max ram it can
handle[2Gb], is incredibly slow with Windows 7 installed, and far from being real time each change builds up in blocks over about 3 minutes.
Thanks again
raymo
Pushing 80????? Holy crap! you are doing an excellent job of digital imaging Raymo, even with very short subs! Nice work!!!!
Tell you what, I have sort of figured out how to get a stretched image out of DSS with some colour and nice details with some tweaking, if you Private Message me your phone number I can help you over the phone (as my Australia wide landline and mobile calls are free from my home phone) and I have 20 years experience with helpdesk calls and customers with even less computer skills than you have and I can hopefully get you to save the settings in DSS so that you can repeat the process MUCH more easily than you probably currently do now.
My patience level is quite large, so don't feel like you are putting me out, I would be more than happy to help you out and give you some tips in DSS as I banged my head on this for a number of months and now I think (to some degree) I have cracked it somewhat and can get nice results out of DSS without any further processing being needed to be done.
Let me know by PM, or (no disrespect intended) if you prefer, simply let me know on this thread and I can PM you with my details so you can call me and then I can step you through the loading, processing and stretching process I use in DSS to get more out of a picture than what it spits out when you leave it all at default.
No problems if you don't want to, by the way, the offer is open to anyone else who wants some tips on DSS. I use DSS beta 3.3.3 if you need any help, please let me know here or via PM and I can call you to run you through either over the phone, or via remote control of your PC (safe, don't worry) how to stretch and "minimally process" your pics.
Sometime in the future, I may take the time to write up a quick "how to" article for reference, but in the meantime, my current after work boredom level is enough to allow me to make this offer to anyone who may need a hand.
Thanks Jo and Rusty. If you are surprised at what I did with DSS,
consider that my laptop is about 8yrs old, has the max ram it can
handle[2Gb], is incredibly slow with Windows 7 installed, and far from being real time each change builds up in blocks over about 3 minutes.
Thanks again
raymo
no wonder it has been tough going! if you can get an external program (like photoshop) to work it will be a whole lot easier to process
Alistair; I tried to save the unadjusted image, but DSS would only
save it in the format "DSS Settings". Windows won't open it so I can resize it if necessary, so I have no idea how to get it into IIS.
raymo
Ray, use the "save image to file" option on the left, to save it as a TIFF file and then right click on it in windows explorer and this will allow you to preview it.
Also, if you right click on the file name, you can select "open with" and then open it with Photoshop, or do it manually using file/open in there. Click on resize image and change it to something like 1024 x 768 and then use the "file/save for web and devices" option. you should be able to then see at the bottom left the JPG SIZE of the file and you can slide the "quality" slider on the top right to the left, to change the compression level. Keep an eye on the size as you move the slider until you see the JPG size go just under 200kb. Then click save and give it a name like "Eta IIS.jpg" so you know it has been resized to suit this website's file size limit. Then upload it like you already have.
Sorry if you already know how to do this, I thought this is what you needed help on from your last post.
I reckon your doing a great job with processing.
Well that kind of explains a few things. DSS seems slow on my i7, let alone a computer that old.
